The invention relates to a laser soldering system for SMD-components.
A system of this type, which operates according to the single-beam method by means of a CW-Nd:YAG Laser and comprises a control device for the rate of change of the temperature, has become known from the DBP 37 012 013 and the EP 0 168 605. The latter system operates by means of an X-Y table and can be moved only in these two axes. The laser spot and the radiation surface as well as the laser power per soldering point are constant; only the laser power intensity is variable. Very narrow temperature--time tolerances must be maintained during laser soldering; specifically the time must be minimal; the temperature must be only barely above the melting point of the solder, but below the disintegration temperature of the substrates and mainly below the thermal damaging of the component, in the present case, predominantly SMD's. The soldering time of the above-mentioned system amounts to over 0.1 sec. per soldering point and, in the case of circuits with high-poled components or numerous soldering points, comes close to the soldering time of the simultaneous die soldering method and reflow strip soldering method. A similar situation exists in the embodiment according to the U.S. Pat. No. 4,845,335.
It is an object of the present invention to provide a system of the initially mentioned type in which the soldering times are shortened so significantly that also high-poled components (SMD's) and circuits with many components may be subjected to an economical laser soldering. Very brief soldering times with correspondingly high laser powers, in order to avoid overheating, require temperature controls as well as an optimizing of the Z-adjustment of the laser lens system and of the radiation surface so that the laser power can be controlled for each soldering point.
This object is achieved according to the invention by a laser soldering system having two computer controlled robotic devices wherein the power of the laser source and its vertical positioning as well as a filler wire advance system are adjustable to control the soldering process.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.